Method for image analysis

ABSTRACT

A method for synthetic data generation and analysis including: determining a set of parameter values; generating a scene based on the parameter values; rendering a synthetic image of the scene; and generating a synthetic dataset including a set of synthetic images.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 62/555,202, filed 7 Sep. 2017, and U.S. Provisional Application Ser.No. 62/571,422, filed 12 Oct. 2017, which are each incorporated hereinin their entirety by this reference.

TECHNICAL FIELD

This invention relates generally to the image analysis field, and morespecifically to a new and useful method for generating and utilizingsynthetic data in the image analysis field.

BACKGROUND

Large datasets are important for implementing machine learning (ML)solutions. In particular, many methods use models having large numbersof parameters, which often require large amounts of data foroptimization. Supervised learning relies upon these large datasets beingexplicitly labeled. However, labeling the data is typically performedwith a human in the loop, whether partially (e.g., checked) by human orperformed entirely manually by a human. This aspect can make thegeneration of suitable datasets time consuming and expensive.Furthermore, labeled datasets that are collected from real worldscenarios are subject to the random nature of real world events.Accordingly, collecting real-world datasets with suitable coverage ofthe parameter space underlying a model can be prohibitively timeconsuming and complex, and in many cases the coverage is difficult toquantify or determine precisely. In addition, methods for producingsynthetic datasets to mitigate issues with real datasets often employ avirtual world (e.g., a single virtual world, a limited number ofholistically-generated virtual worlds, etc.) in which a virtual camerapositioned and used to generate synthetic images. However, this approachcan yield datasets where some environmental parameters are constant orinadequately varied throughout, due to the limited nature of the virtualworld. The resultant datasets can also suffer from: poor image quality,poor realism (e.g., manifesting as a large “domain shift” between thereal and synthetic images), requiring “fine tuning” (e.g., training onsynthetic, then real, images to fine tune the neural networks, adjustingthe training data manually to improve performance, etc.), one-offvirtual world creation (e.g., generalized scene configurationscorresponding to an explorable virtual world instead of unique sceneconfigurations), and insufficient parameter variation (e.g., varying toofew image parameters, such as time of day, weather, etc.) Often, thearchitecture of computational paradigms for generating typical virtualworlds (e.g., gaming engines) do not adequately generate wide andefficient variability over the underlying parameter space, due to thedivergence between the needs of common use cases (e.g., game play) andthose of synthetic datasets for ML model use.

Thus, there is a need in the field to create a new and useful method ofgenerating synthetic image datasets depicting simulated real-worldimagery, that are intrinsically labeled, and efficiently cover theparameter space underlying machine learning models. This inventionprovides such a new and useful method.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A depicts a flowchart of an example implementation of the method;

FIG. 1B depicts a schematic diagram of an example implementation of themethod;

FIG. 2 depicts an example of a joint probability distribution functionof a pair of parameters associated with an example implementation of themethod;

FIG. 3 depicts a comparison of a low-discrepancy sequence of subrandompoints and a set of random points;

FIG. 4 depicts a schematic illustration of an example implementation ofthe method;

FIG. 5 depicts an example of intrinsic semantic segmentation of outputsynthetic images of an example implementation of the method; and

FIG. 6 depicts a schematic diagram of an example implementation of aportion of a variation of the method.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments of the inventionis not intended to limit the invention to these preferred embodiments,but rather to enable any person skilled in the art to make and use thisinvention.

1. Overview

As shown in FIGS. 1A-1B, the method 100 can include: determining a setof parameter values associated with at least one of a set of geometricparameters, a set of rendering parameters, and a set of augmentationparameters S100; generating a three dimensional (3D) scene based on theset of geometric parameters S200; rendering a synthetic image of thescene based on the set of rendering parameters S300; and, generating asynthetic image dataset S500. The method can additionally oralternatively include: augmenting the synthetic image based on the setof augmentation parameters S400; training a model based on the syntheticimage dataset S600; evaluating a trained model based on the syntheticimage dataset S700; and/or any other suitable method blocks orsubprocesses.

The method 100 functions to generate synthetic data that is suited(e.g., optimally suited, adapted to optimize model convergence and/oraccuracy, etc.) to image-based machine learning (e.g., computer visionmodels, vehicle control models, classification models, mission planningmodels, etc.). The images can include optical images, but canadditionally or alternatively include other suitable data that isrepresentable as a projection of a three-dimensional (3D) space (e.g.,LIDAR, radar, point clouds, etc.). The method 100 can also function tomaximize the coverage (e.g., of a multidimensional parameter space;e.g., how many different kinds of scenarios or types of objects are in aset of images, such as whether there is a child crossing the streetbehind a bus) and variation within a scene (i.e., a virtual 3D space;e.g., distribution, or how many different instances are present acrossall categories represented in the coverage, such as whether the datasetincludes a child crossing the street behind the bus in the morning,evening, and night) given a set of parameters that control the creationof a 3D scene and virtual image generation of the 3D scene. The method100 can also function to procedurally generate the geometry of streetscenes for capture via synthetic imagery (e.g., images of the virtualstreet scenes). The method 100 can also function to maximize thecoverage of a multidimensional parameter space that defines renderingand/or augmentation of images depicting a 3D scene. The method 100 canalso function to generate a synthetic dataset for provision to a thirdparty (e.g., a developer of machine image classification models, atester of computer vision models, a creator of vehicle control modelsbased on image analysis, etc.). However, the method 100 can additionallyor alternatively have any other suitable function in relation tosynthetic data generation and/or analysis.

The method 100 is preferably performed by, executed at, and/orimplemented at a computing system. The computing system can include aremotely interconnected set of computing modules (e.g., a cloud basedcomputing system, one or more CPUs, one or more GPUs, etc.).Additionally or alternatively, the computing system can include avehicle computing system (e.g., a vehicle ECU, central vehicle computer,etc.). However, the method can be otherwise implemented at any suitablecomputing system and/or network of computing systems.

The method 100 can have several applications. In a first exampleapplication, the method can be used to train a new model (e.g., amachine learning model) for image analysis (e.g., classification ofobjects in images, determination of the properties of objects in images,etc.). In a second example application, the method can be used toimprove and/or augment a model that has been previously trained onreal-world, “organic” data (i.e., not synthetic) with additional datavolume derived from synthetic data. In a third example application, themethod can be used to validate a trained model (e.g., after modelgeneration and/or training) for consistency (e.g., to demonstrate thatthe model will perform predictably when previously unseen data isprovided as a model input) and/or accuracy (e.g., to benchmark the modeloutput against known ground truth data, either intrinsically known fromthe synthetic data, manually generated for real-world data, or otherwisesuitably obtained). However, the method 100 can have any other suitableapplications.

Inputs to the method can include user preferences (e.g., a set ofparameters relevant for training a machine learning model), a geographiclocation identifier (e.g., a location associated with known parametervalues or ranges of parameter values), a temporal identifier (e.g., atime of day associated with known parameter values or ranges ofparameter values), and any other suitable inputs. Output of the methodpreferably includes a synthetic dataset that includes realistic (e.g.,closely approximating the real-world), intrinsically labeled (e.g.,during procedural generation of the dataset) images for training and/orevaluating the performance of image-based machine learning models. Themethod can additionally or alternatively output three-dimensionalscenes, four-dimensional scenes (e.g., a time series of 3D scenes), andany other suitable outputs.

2. Benefits

Variants of the method can afford several benefits and/or advantages.First, variants of the method can generate large numbers of differentimages that maximize the coverage of the dataset (e.g., the number ofdifferent types of scenarios, scenes, and/or object types that are inthe set of images, the coverage of the dataset over the span of themultidimensional parameter space underlying the dataset, etc.) given thenumber of images and a set of parameters to vary within the number ofimages. Whereas real-world datasets can have indeterminate coverageand/or coverage that is difficult to quantify, variants of the methodautomatically produce synthetic datasets having maximal coverage that isexplicitly quantified. In addition, variants of the method includegenerating a unique scene for each synthetic image (instead of changingthe viewpoint of a virtual camera within a single scene to generate aseries of images) in order to efficiently cover the parameter space ofthe virtual domain. Accordingly, variations of the method maximizeparametric variation within a finite-size dataset. Whereas imagecreation (e.g., in film, in animation, etc.) in conventional solutionstypically aims to produce a sequence of temporally correlated orotherwise related images (e.g., an animation, a gameplay environment,etc.), variations of the method 100 afford the benefit of producingsynthetic datasets including images that are maximally diverse acrossthe set of variable parameters underlying image production and thus ofparticular use in the context of ML models that learn optimally fromdiverse data.

Second, variants of the method result in labels of objects (and poses ofsuch objects) within synthetic images that are inherently “perfect”(e.g., as accurate as possible) without human or other manualintervention (e.g., human-derived object or pose labels), because objecttypes, layouts, relative orientations and positions are deterministicand known due to programmatic (e.g., procedural) generation of thevirtual scene containing the objects. For example, hand-annotated datain conventional, manually-generated labeled datasets can fail to trainML models (e.g., networks) to recognize objects that are not correctlyannotated in the ground-truth datasets (e.g., the hand-annotateddatasets), whereas an intrinsically-labeled, procedurally generatedsynthetic dataset generated in accordance with variants of the method100 are programmatically prevented from containing annotation errors.FIG. 5 depicts an example of pixel-by-pixel segmentation (e.g.,intrinsic labeling) of synthetic images based on the underlying objectsand/or groups of objects. Intrinsically labeled data can also be used,in examples, for validation of models, for exploration of novel MLarchitectures, and for analysis of trained models.

Third, variants of the method generate high quality images that depictrealistic road scenes, which minimizes the “domain shift” between thesynthetic image dataset and real-world images. The result of training amodel using a synthetic dataset having minimal domain shift fromreal-world datasets is a trained model that performs significantlybetter when implemented using real-world data, but that can also beefficiently trained using automatically generated synthetic data. Inaddition, variants of the method can enable the elimination or reductionof fine tuning in cases wherein a model is trained on synthetic data,and then subsequently using real-world data to tune model behavior(e.g., outputs of the model) to the target domain. In conventionalapproaches, neither weight initialization nor fine tuning cansufficiently mitigate domain shift of datasets with poor realism. Incontrast, variants of the method 100 can be used to produce high qualitysynthetic data wherein the realism is engineered directly into the dataitself via procedural control of aspects of realism (e.g., orthogonalaspects of realism) including overall scene composition, geometricstructure, illumination by light sources, material properties, opticaleffects, and any other suitable aspects of image realism.

Fourth, variants of the method can enable testing and validation ofpreviously-trained models. Synthetic datasets generated via the methodcan provide consistent, well-labeled testing and validation datasetsagainst which a model (e.g., a neural network) can be run (e.g., havethe synthetic data provided as inputs) repeatedly to ensure that itsperformance characteristics (e.g., outputs, classification accuracy,recognition accuracy, etc.) stay within an expected range, which canallow regression testing (and other tests) to be performed.

Fifth, variants of the method can enable performance analysis of models.Models (e.g., neural networks, convolutional neural networks, deeplearning networks, other ML networks, etc.) trained on real-world datacan be difficult to analyze, due to unpredictability of the trainedmodel parameters. When synthetic datasets generated via the method areprovided to such models, the parameter set associated with each of thesynthetic images (e.g., predetermined and known parameter values foreach parameter used to generate the synthetic images) can provideinsights into the states (e.g., the collection of parameter values andranges thereof) and combinations thereof for which a model performsappropriately (e.g., classifies accurately) and for which it does not.This performance data can be used to tune the model, to seek outadditional real world data having specified parameters based on theresults of the performance analysis, or for any other suitable purpose.

Sixth, variants of the method can reduce or prevent overfitting oflearning networks (e.g., neural networks) by performing dataaugmentation (e.g., during or prior to training) in a manner thatminimizes undesirable correlation between augmented samples (e.g., thatcan arise from randomly applying data augmentation). For example,synthetic images can be augmented (e.g., scaled, translated, brightened,and/or darkened, etc.) by a parameterized factor, for which the value(e.g., for each image, for each sample, etc.) is determined by samplinga low-discrepancy sequence (LDS). Additionally or alternatively,undesirable correlation between any successive steps of synthetic imageproduction can be minimized by parametrizing variables that vary betweenthe successive steps and sampling the variables from an LDS (e.g.,choosing which of a plurality of generated scenes is used for renderingbased on a selection parameter sampled from an LDS) to provide thebenefit of minimizing correlation between generation steps.

Seventh, variants of the method can split processing into multiplestages to maximize computational efficiency by separating independentsynthetic image generation subprocesses. For example, adjusting a cameraexposure parameter during image augmentation (e.g., in accordance withone or more variations of Block S400) does not affect the flow ofphotons in a scene (e.g., determined during rendering the image inaccordance with one or more variations of Block S300) or the placementof vehicle objects (e.g., determined during programmatic scenegeneration in accordance with one or more variations of Block 200), andthus can be efficiently performed at a later stage of the generation andanalysis process.

Eighth, variants of the method can confer improvements incomputer-related technology (e.g., image processing, image generation,image analysis, computer vision, vehicle control models, etc.) byleveraging non-generic, realistic synthetic image data (e.g., generatedin accordance with one or more variations of the method), In examples,the technology can confer improvements in the application of suchtechnology by enabling efficient (e.g., computationally efficient,temporally efficient, etc.) and/or accurate model training or evaluationperformance exceeding that of real-image data alone or instead.

Ninth, variants of the method can provide technical solutionsnecessarily rooted in computer technology (e.g., classifying objects inimages according to machine classification rules and/or models,extracting semantic information from images, etc.) to overcome issuesspecifically arising with computer technology (e.g., overfitting issues,convergence issues, inadequate synthetic data issues, insufficienttraining data issues, etc.). In another example, the method can includeapplying computer-implemented rules (e.g., parameter sampling rules tominimize undesirable auto- and cross-correlation between variablesetc.).

Tenth, variants of the method can confer improvements in the functioningof computational systems themselves. For example, the method can improveupon the processing of generated synthetic data (e.g., by intrinsicallylabeling the objects depicted in synthetic image to speed convergence oftrained models to accurate outputs and reduce computational and/ormanual labeling expense).

However, the method and variants thereof can afford any other suitablebenefits and/or advantages.

3. Method

As shown in FIGS. 1A-1B, the method 100 can include: determining a setof parameter values associated with at least one of a set of geometricparameters, a set of rendering parameters, and a set of augmentationparameters S100; generating a three dimensional (3D) scene based on theset of geometric parameters S200; rendering a synthetic image of thescene based on the set of rendering parameters S300; augmenting thesynthetic image based on the set of augmentation parameters S400; and,generating a synthetic image dataset S500. The method can additionallyor alternatively include: training a model based on the synthetic imagedataset S600; evaluating a trained model based on the synthetic imagedataset S700; and/or any other suitable method blocks or subprocesses.

The method 100 functions to generate synthetic data that is suited(e.g., optimally suited, adapted to optimize model convergence and/oraccuracy, etc.) to image-based machine learning (e.g., computer visionmodels, vehicle control models, classification models, mission planningmodels, etc.). The images can include optical images, but canadditionally or alternatively include other suitable data that isrepresentable as a projection of a three-dimensional (3D) space (e.g.,LIDAR, radar, point clouds, etc.). The method 100 can also function tomaximize the coverage (e.g., of a multidimensional parameter space) andvariation within a scene (i.e., a virtual 3D space) given a set ofparameters that control the creation of a 3D scene and virtual imagegeneration of the 3D scene. The method 100 can also function toprocedurally generate the geometry of street scenes for capture viasynthetic imagery (e.g., images of the virtual street scenes). Themethod 100 can also function to maximize the coverage of amultidimensional parameter space that defines rendering and/oraugmentation of images depicting a 3D scene. The method 100 can alsofunction to generate a synthetic dataset for provision to a third party(e.g., a developer of machine image classification models, a tester ofcomputer vision models, a creator of vehicle control models based onimage analysis, etc.). However, the method 100 can additionally oralternatively have any other suitable function in relation to syntheticdata generation and/or analysis.

3.1—Defining and Sampling Parameter Space

Block S100 includes determining a set of parameter values associatedwith at least one of a set of geometric parameters, a set of renderingparameters, and a set of augmentation parameters. Block S100 functionsto define the parametric rule set for 3D scene generation, imagerendering, and image augmentation. Block S100 can also function tomaximize coverage of a parameter space associated with a parameter(e.g., by sampling the value of the parameter from an LDS) given afinite number of samples (e.g., synthetic images, data samples, etc.).Block S100 can also function to sample the parameter space that candefine a virtual three-dimensional scene made up of instances of objectclasses, wherein the parameter space can be infinite, semi-infinite,discretely infinite, or finite, in an efficient manner that enablessubstantially maximal coverage of the parameter space (e.g., given afinite number of samples, with each incremental sample, etc.). BlockS100 is preferably implemented by a computing system, but canadditionally or alternatively be implemented using any other suitablecomponent.

In relation to Block S100, all aspects of the individual object classes,such as geometry, materials, color, and placement can be parameterized,and a synthesized image and its corresponding annotations (e.g., of eachinstance of an object class in a virtual scene) represent a sampling ofthat parameter space (e.g., multidimensional parameter space).Furthermore, aspects of the image rendering and post-renderingaugmentation of the image can be parameterized, and the sampling ofthese parameterized aspects (e.g., to generate rendering parametervalues, augmentation parameter values, etc.) can represent the samplingof that parameter space and/or further dimensions of the parameter spacedefining aspects of the object classes in a virtual scene.

Block S100 is preferably performed multiple times within an iteration ofthe method 100 (e.g., between other Blocks of the method). For example,the method can include: determining a set of geometric parameters andsampling corresponding values, and generating a 3D scene based on thevalues of the geometric parameters; subsequently determining a set ofrendering parameters and sampling corresponding values, and rendering animage of the 3D scene based on the values of the rendering parameters;and subsequently determining a set of augmentation parameters andsampling corresponding values, and augmenting the image of the 3D scenebased on the values of the augmentation parameters. Block S100 canadditionally or alternatively be performed a single time within aniteration of the method 100: for example, the method can includedetermining and sampling a multidimensional parameter space thatincludes geometric parameters, rendering parameters, and augmentationparameters prior to scene generation, rendering, and/or augmentation.However, Block S100 can additionally or alternatively be performed withany other suitable temporal characteristics relative to other Blocks ofthe method 100.

Block S100 can include determining an object class, which functions toselect a class of object to be included in the parametric scenegeneration (e.g., in accordance with one or more variations of BlockS200). Block S100 can include determining a set of object classes to bedepicted in a 3D scene. Determining the set of object classes caninclude selecting from a predetermined list of possible object classes(e.g., automotive vehicles, pedestrians, light and/or human-poweredvehicles, buildings, traffic signage or signals, road surfaces,vegetation, trees etc.). Determining the set of object classes can bebased upon received instructions (e.g., user preferences, preferences ofan entity requesting generation of a synthetic dataset, etc.),contextual information (e.g., the physical environment of which thesynthetic image dataset is intended to be representative), or otherwisesuitably determined with any other suitable basis. The set of objectclasses can be different for each scene, and can include various subsetsof the list of possible or available object classes (e.g., wherein afirst scene includes only automotive vehicles, and a second sceneincludes only traffic signage and buildings, etc.). The object classesare preferably associated with traffic objects (e.g., objects that arefound in realistic environments traversed by a vehicle in typicalvehicle operation scenarios), but can additionally or alternativelyinclude any suitable three-dimensional objects that can be arrangedwithin a virtual world (e.g., imaginary objects, objects having a lowprobability of occurrence in the real-world such as a large inflatableparade balloon, etc.). In some examples, the object classes defining thelist of possible object classes for inclusion can be extracted from areal world dataset (e.g., via an object detection and classificationprocess), such as a real world cityscape dataset; in such examples andrelated examples, determining the list of object classes can includereplicating the list of object classes extracted, selecting a subsetfrom among the extracted object classes (e.g., to increase thelikelihood of low-probability object classes of appearing in thesynthetic dataset), or otherwise suitably determining the object classor set of object classes for inclusion.

Block S100 can include defining a portion of the set of parametersassociated with the object classes to be depicted in a scene. Theseparameters can include geometric parameters (e.g., size,three-dimensional position, three-dimensional orientation or attitude,etc.), selection parameters (e.g., wherein one or more object classesare associated with predetermined 3D models from which an instance ofthe object class to be included in a virtual scene is selected), anumerosity of one or more object classes, and any other suitableparameters describing the virtual arrangements and/or orientations ofinstances (e.g., objects) of the object classes to be included in avirtual scene (e.g., scene parameters).

Block S100 can, in variations, include determining an entire set ofparameters defining a multidimensional parameter space that encompassesscene parameters, rendering parameters, and augmentation parameters. Theparametrized variables (e.g., parameters) used in subsequent Blocks ofthe method can be known or determined prior to the generation of a scene(e.g., Block S200), rendering an image of the scene (e.g., Block S300),and/or augmenting of the image (e.g., Block S400); for example, prior toscene generation, Block S100 can include determining which augmentationparameters (e.g., camera exposure, scaling ranges, etc.) will sampledand used in generating the synthetic image dataset. However, inalternative variations, Block S100 can include determining any suitablesubset of the set of parameters at any suitable relative time relativeto other Blocks or portions of the method 100.

Block S100 includes determining a set of parameter values of thedetermined parameters (e.g., sampling a value of each of the set ofparameters from a distribution function associated with each parameterand/or group of parameters). Parameters can include any quantifiableproperty of a virtual scene. Preferably, the parameters are related todriving-relevant environments (e.g., roadways and surrounding objectsand scenery), but can additionally or alternatively be related to anysuitable virtual environment (e.g., airplane landing and takeoffcorridors, orbital trajectories, pedestrian routes, mixed useenvironments, etc.). Each parameter of the set of parameters can take ona value that is defined by a random variable, which can each be ofseveral types: discretely valued (DV) random variables, stochasticallyvalued (SV) random variables, and continuously valued (CV) randomvariables. DV parameters are preferably selected from a predeterminedset or range (e.g., a set of discrete numerical values, a set ofpredetermined 3D model descriptions, etc.), but can be otherwisesuitably determined. In a specific example, a DV parameter can be avehicle object parameter, which can take on one of 30 predeterminedvalues (e.g., 3D models of various vehicle types), and the parametervalue can be sampled from the set of 30 3D models in order to maximizethe coverage of the set within the generated scene. CV parameters arepreferably determined from either a discrete or continuous distributionof values based on a randomized seed (e.g., computed as a pseudorandomnumber), but can be manually selected, automatically extracted from amap or image (e.g., of a real-world scene, of a physical location, of amanually or automatically detected edge case), or otherwise suitablydetermined. CV parameters are preferably computed from a continuousfunctional distribution (e.g., a single valued function), but can beotherwise suitably determined. In one example, DV parameters aredetermined for a set of candidate objects (e.g., pedestrians, roads,light source, etc.); and CV parameter values and SV parameter values aredetermined (e.g., selected, specified, received, randomly generated,etc.) for each candidate object to be included in the scene (e.g., basedon a set of potential values associated with each candidate object). Ina specific example, the discrete variables include: an overall number ofpedestrians in the scene, a wet road surface, and light; the continuousvariables include: the camera location (e.g., x/y/z), each pedestrian'sheight and pose, and the angle and magnitude of the light (e.g., intothe camera); and the stochastic variables include: the pedestrianlocations within the scene (e.g., wherein the stochastic variable can bechanged between images to produce scenes with the desired parametricproperties but with unique combinations).

Examples of parameters for which values are determined in Block S100include: roadway numerosity and connectivity, roadway spacing (e.g.,space between intersections, width of roadways, length of roadways, lanespacing on roadways, number of lanes, road width, etc.), ground and/orroadway surface properties (e.g., roughness, reflectivity, trafficmarkings, repair markings, material, moisture, etc.), sidewalkproperties (e.g., presence or absence of sidewalks, curb height, width,surface properties, color, material, dirt amount, etc.), surroundingobject properties (e.g., presence or absence of buildings, pedestrians,fences, cars, vegetation, etc.) and properties associated therewith(e.g., height, width, window height, depth, material, numerosity, color,surface characteristics, orientation, position, geometric model, type,count, etc.), objects on the roadway (e.g., motor vehicles,human-powered vehicles, sedans, vans, trucks, etc.) and propertiesassociated therewith (e.g., numerosity, color, surface characteristics,orientation, position, etc.), lighting parameters (e.g., practicallighting such as traffic lights or street lights, atmospheric lighting,longitude and latitude dictating sun positions, direction, angle,intensity, color, cloud cover, etc.), or any other suitable parameter.Further examples of parameters can include absolute or relative amountsof object categories (e.g., proportion of buildings to pedestrians, ofpedestrians to cars, cars to bicyclists, etc.), predetermined 3D modelproperties (e.g., width of a road model, number of lanes of a roadmodel, whether there is a median present in the road model, etc.), andother object properties (e.g., number of floors of a building,architectural style of a building, setback from the street in relativeor absolute dimensions corresponding to a virtual scene, etc.).Positions of each object can be defined by parameters (e.g., relative tocamera position and orientation, relative to global coordinates, byspecifying coordinates, heading, orientation, drag and drop, etc.).Objects that are defined by scene parameters can be made up ofsubobjects, which can have properties (e.g., defined by parameters,which can be the same parameters, similar parameters, or differentparameters than the parent object) associated therewith. For example, abuilding object can include a footprint (e.g., defined by a DV parameterthat can take on a value of a footprint selected from a set ofpredetermined building footprints) and a number of floors and windows,each of which can be defined by additional parameters. However, sceneparameters can include any suitable parameters to define any suitableobjects representable within a scene.

Block S100 is preferably performed prior to generating a scene, but canalternatively be performed concurrently with scene generation (e.g.,real-time generation and/or rendering) or at any other suitable time.Preferably, a new set of parameter values is determined (e.g., sampledfrom an LDS) each time a scene is generated, and then a synthetic imageis generated of the newly generated scene (e.g., wherein a camera angleand position is defined by a pair of parameter values that are sampledto maximize the coverage of the parameter space). Alternatively, asingle scene is generated, and the parameters defining the viewpoint ofa virtual camera (e.g., camera angle and position of the camera) can bechanged within the scene to generate a set of synthetic images. However,Block S100 can have any other suitable temporal characteristics.

The output(s) of Block S100 preferably include the definition of eachobject property (e.g., defined by parameter values) as well as thelayout of each object within the scene (e.g., defined by parametervalues), which can be used to generate the three dimensional virtualrepresentation in Block S200.

Block S100 preferably includes determining a probability densityfunction (PDF) for each parameter of the set of parameters, and samplingthe PDF to obtain the value of the parameter (e.g., the parametervalue). Each parameter value preferably assumes a value within the range[0,1], and can be remapped after sampling to a range suitable for theproperty that the parameter describes (e.g., to a range of 0-8″ for curbheight, to a range of 15-50′ for roadways, etc.). Alternatively, theparameters can assume a value within any suitable range. The PDF can beuniform (e.g., a line), normal (e.g., a Gaussian), discrete orcontinuous, or have any other suitable functional shape or mathematicalproperties. The PDFs of multiple parameters can be coupled together(e.g., to form a joint PDF as shown in FIG. 2). In a first variation,the PDF of each parameter can be selected by a user (e.g., via anexplicit choice by a human operator, available variables that areselected manually for each scene, object, and/or set of objects, etc.).In a second variation, the PDF of each parameter (or of a subset of theset of parameters) can be a learned function that is based on the outputof training a model on the synthetic dataset, a real dataset, and/or acombination of synthetic and real data (e.g., the PDF of one or moreparameters can be tuned to improve the performance of the model).

In variations, specific object classes can be associated with aplurality of predetermined 3D models. For example, a vehicle objectclass can include a set of 3D models of various vehicle makes (e.g.,manufacturers), models (e.g., corresponding to specific models of aparticular manufacturer), types (e.g., personal vehicles, commercialtrucks, etc.), and the like. In another example, each time an instanceof a car object is inserted into a scene or designated for inclusion ina scene, the instance can be chosen from a library of different types ofcars (e.g., 200 types of cars, 50 types of cars, etc.). In anotherexample, as shown in FIG. 6, Block S100 can include selecting a frame ofan animation loop associated with an actor or animated person via aselection parameter sampled from an LDS, wherein each frame of the loopis associated with a map value, and matching the map value and theselection value selects the frame of the animation (e.g., 3D animation)for insertion into a scene. The set of 3D models can be mapped to a setof map values (e.g., within the range [0,1]) that can then be sampledfrom (e.g., based on matching a selection parameter value sampled froman LDS to a map value) to determine which of the set of 3D models to usefor a particular instance of the object class. Some object classes ofthe set of object classes represented in a scene can be entirelyprescribed by geometric parameters (e.g., height, width, depth, shapefunctions, etc.) whereas others (e.g., a subset of the set of objectclasses, a second set of object classes selected from the set of objectclasses, etc.) can correspond to associated sets of predetermined 3Dmodels (e.g., associated with map values between 0 and 1 or with anyother suitable map values that enable efficient selection of apredetermined 3D model from a set of available 3D models according to anLDS or other suitable sampling method).

Each parameter value (e.g., of each parameter of the set of parameters,each geometric parameter, each selection parameter, each renderingparameter, each augmentation parameter, any other parameter associatedwith a variable of the 3D scene and related synthetic images, etc.) ispreferably determined (e.g., sampled, selected, computed, generated)according to a low discrepancy sequence (LDS) that covers the range ofpossible and/or allowable parameter values. A suitable LDS preferablyhas the property that for all values of N, its subsequence x₁, . . . ,x_(N) has a low discrepancy. An LDS may also be referred to as aquasi-random sequence or subrandom sequence. An LDS is preferably not arandom sequence or a pseudorandom sequence, but can share someproperties of random sequences. An LDS or equivalent set of points ispreferably constructed such that for each additionally sampled point inthe sequence, the coverage of the parameter space (e.g., allowable rangeof values of the parameter, [0,1], etc.) is maximized as compared to asimilar random or pseudorandom sequence (see, e.g., FIG. 3). Forexample, the parameter value can be sampled from the PDF at a pointcorresponding to a Halton sequence, Sobol sequence, Faure sequence,Reverse Halton sequence, Niederreiter base 2 sequence, Niederreiterarbitrary base sequence, Poisson disk sampling, Hammersley set, van derCorput sequence, an additive recurrence sequence, a negativelycorrelated random number sequence, and/or any other suitably constructedLDS.

In variations, each LDS used in association with sampling any of theaforementioned parameters is a Sobol sequence. In alternativevariations, a first LDS can be a Sobol sequence, a second LDS can be aHalton sequence, and a third LDS can be a Hammersley sequence. In somevariations, the type of LDS can be determined based on the parametertype (e.g., a geometric parameter can be selected according to samplingof a Sobol sequence, a rendering parameter can be selected according tosampling of a Halton sequence, and an augmentation parameter can beselected according to a Hammersley sequence). However, sampling ofparameter values can be otherwise suitably performed according to anysuitable LDS sequence, other sequence, or continuous parametricfunction.

Alternatively, each parameter value can be determined by sampling thePDF with a random or pseudorandom sequence, using any suitable random orpseudorandom sampling technique.

In a specific example, a first instance of Block S100 includesdetermining a geometric parameter, wherein the geometric parameterdefines a first parameter space, and sampling the first parameter spaceaccording to a first low discrepancy sequence (LDS) to generate ageometric parameter value. In this specific example, a second instanceof Block S100 includes determining a rendering parameter, wherein therendering parameter defines a second parameter space, and sampling thesecond parameter space according to a second LDS to generate a renderingparameter value. In this specific example, a third instance of BlockS100 includes determining an augmentation parameter, wherein theaugmentation parameter defines a third parameter space, and sampling thethird parameter space according to a third LDS to generate anaugmentation parameter value.

Block S100 can optionally include constraining parameter values anddetermining parameter values based on the constraint(s) (e.g.,constrained values). For example, in a case wherein the parameterdefines the orientation (e.g., heading) of an object, the orientationcan be constrained to align substantially with a direction of trafficflow. In a related example, bicycle objects can be selected from a setof predetermined models (i.e., the bicycle objects types are a discretevariable) and then positioned along a defined roadway (e.g.,stochastically by sampling a stochastic variable), but can take on anorientation defined by a continuous variable that is constrained to beno more than 5° from parallel with the traffic direction of thevirtually defined roadway. However, the parameter values can beotherwise suitably constrained or unconstrained. Value constraints caninclude constraining a parameter resolution (e.g., limiting a resolutionof one or more parameter spaces of a plurality of parameter spaces toreduce a dimensionality of the resulting synthetic image data set) to bebelow a threshold resolution (e.g., number of samples over the range ofthe parameter). In a specific example, Block S100 can include limiting aresolution of one or more parameters based on a computational constraint(e.g., defining a maximum resolution available for variation of one ormore parameters). In another example, Block S100 can include limiting aresolution of one or more parameters based on a relative importance ofeach parameter (e.g., based on user preferences, third party recipientpreferences, frequency of one or more object classes in a real-worlddataset wherein more frequently appearing object classes are varied at ahigher resolution and vice versa, etc.). In another example, Block S100can include selecting a subset of generated 3D scenes from which torender a plurality of 2D images (e.g., wherein the parameter for whichresolution is limited is a selection parameter corresponding to theselection of a 3D scene for rendering). However, Block S100 canadditionally or alternatively include otherwise suitably constrainingone or more parameters.

In related variations, Block S100 can include constraining parametervalues based on extracted parameter ranges. In examples, the method caninclude extracting (e.g., from a real image dataset, from a database,etc.) a set of parameter ranges (e.g., maximum and minimum parametervalues in a real image dataset) and constraining parameter values (e.g.,sampled from an LDS) to fall within the extracted parameter range (e.g.,by remapping the sampled LDS value to be between the minimum and maximumvalues of the range). In a specific example, the minimum and maximumcamera exposure can be extracted from a real-image dataset, and anaugmentation parameter defining a camera exposure (e.g., imagebrightness and/or contrast) can be constrained to fall between theminimum and maximum camera exposure upon sampling the parameter valuefrom an LDS.

Block S100 can optionally include grouping parameters, and determiningthe values of the grouped parameters (e.g., by sampling an LDS to map asingle sampled value of the LDS onto a coupled parameter valuescorresponding to a group of parameters). Grouping parameters functionsto reduce the dimensionality of the parameter space, and can alsofunction to separate groups of variables from one another in caseswherein certain parameters are not suitable for combination into a jointPDF. The grouped parameters can be: related, unrelated, the variedparameters (e.g., randomized parameters, parameters for which randomvalues are determined), a varied parameter with a set of staticparameters, parameters selected by a user, randomly selected parameters,or be any suitable set of parameters. In a first example, in a casewhere a scene includes parameters that define a random viewpoint and arandom position for a car object within the scene, two separate LDSs canbe constructed wherein a first LDS includes a set of 3 parameters (e.g.,variables) defining the viewpoint, and a second LDS includes a set of 2parameters defining the car object (e.g., the two dimensional extentholding a third dimension constant). In alternative implementation ofthe above case, a single LDS having 5 dimensions (e.g., onecorresponding to each parameter) can be constructed, and points of theparameter space sampled across the 5 dimensions to maximize coverage.

In variations of Block S100 including grouping parameters into parametergroups prior to sampling, the order of the groupings during theconstruction of the LDS is preferably randomly selected (e.g., such that2 sets of 3D LDSs do not generate the same sequence). For example, arandom digit offset of the sample index can be used to ensurerandomization between LDS sampling. However, points can be selected fromthe grouped-parameter-based LDS according to any suitable decorrelatingtechnique.

In variations of Block S100 including sampling of multiple parameters(e.g., sampling a multidimensional parameter space), decorrelatingtechniques can be used. For example, Block S100 can include applying aconstant offset to an LDS when sampling values, and taking a new sampleas equal to (LDS+offset) modulo 1.0, such that the sampled value iswrapped around in the [0 . . . 1] range (e.g., offsetting a sample indexof each of a set of parameter values, map values, selection parametervalues, etc., by a randomly generated digit or offset between samplingof each of the set of parameter values and each of the set of mapvalues). In another example, the Cranley-Patterson Rotation techniquecan be used to offset the sampling of the LDS according to a randomvector of offset values, and thereby decorrelate the sampling of theindividual points of the LDS. For example, Block S100 can includesampling a multidimensional parameter space and performing aCranley-Patterson rotation between at least two dimensions of themultidimensional parameter space during sampling.

3.2—Scene Generation

Block S200 includes generating a 3D scene based on parameter values(e.g., determined in accordance with one or more variations of BlockS100). Block S200 functions to procedurally create a three dimensionalvirtual representation of an environment (e.g., a scene) based on theparameter values that control the implementation of the procedure (e.g.,geometric parameter values, parameter values defining which objectclasses will be populated into a scene). Block S200 can also function toproduce a realistic virtual scene, wherein realism in the overall scenecomposition, along with the geometric structure and the materialproperties of objects in the scene, is enforced by the parametrized ruleset and parameter values (e.g., determined in an instance of BlockS100). Block S200 is preferably performed subsequently to an instance ofBlock S100 and based on the parameter values determined therein, but canalternatively be performed at any suitable time and based on anysuitable parameter values or procedural rules.

The output of Block S200 preferably includes a three dimensional virtualrepresentation of a set of objects (e.g., a scene), the aspects of whichare defined by the parameter values determined in Block S100. Eachobject in the scene generated in Block S200 is preferably automaticallylabeled with the parameter values used to generate the object (e.g.,including the object class name, object type, material properties,etc.), and other suitable object metadata (e.g., subclassification), inorder to enable the synthetic image(s) generated in Block S300 to beused for supervised learning without additional labeling (e.g., theobjects in the scene are preferably intrinsically labeled). However, thescene can alternatively not include the labels, include any suitablelabels, or include labels to be used for any other suitable purpose.

In variations, Block S200 can include defining the set of parameters tovary as well as the rule set that translates the parameter values (e.g.,sampled according to one or more variations of Block S100) into thescene arrangement. However, the set of parameters to vary canadditionally or alternatively be defined prior to Block S200 (e.g., inan instance of Block S100) or at any other suitable time.

Block S200 preferably produces, as output, a plurality of synthesizedvirtual scenes. Scene synthesis in conjunction with the method 100preferably includes a defined model of the 3D virtual scene (e.g.,determined in accordance with one or more variations of Block S100) thatcontains the geometric description of objects in the scene, a set ofmaterials describing the appearance of the objects, specifications ofthe light sources in the scene, and a virtual camera model; however, themodel of the 3D virtual scene can additionally or alternatively includeor omit any other suitable components or aspects (e.g., the virtualcamera model can be defined when rendering a synthetic image). Thegeometry can be described and/or specified in terms of discretizedrendering primitives (e.g., triangles, polygons, surface patches, etc.),or otherwise suitably described. The materials describing or definingthe appearance of the objects preferably define how light interacts withsurfaces and participating media (e.g., air or dust interposed between avirtual camera and surfaces), but can otherwise suitably define objectproperties. After generation, the scene is then virtually illuminatedusing a light source (e.g., a single light source, several lightsources, etc.), and the composition of the rendered frame is defined byintroducing a virtual camera.

In examples, Block S200 can include generating a plurality of 3D scenes(e.g., based on parameter values corresponding to geometric parameters).The plurality of 3D scenes can be parameterized (e.g., via a set of mapvalues) such that one can be selected (e.g., according to one or morevariations of Block S100) according to an LDS for rendering (e.g.,according to one or more variations of Block S300).

In a first variation, Block S200 includes generating the geometry andlayout of objects in a scene according to the set of parameter valuesassociated with each object in the scene and the interconnectivity(e.g., relative arrangement) of the objects determined in Block S100. Ina specific example, Block S200 includes selecting object geometry ofeach object from a geometry database (e.g., a database of CAD models,geometry gathered from real-world examples of objects in the form ofimages, etc.) and arranging the objects (e.g., rendered using theselected geometry) within a virtual space based on a pose parametervalue (e.g., determined in a variation of Block S100). In anotherspecific example, Block S200 includes placing an object in a 3D scene,wherein the object is an instance of an object class, based on thegeometric parameter value (e.g., defining a spacing of the placed objectrelative to previously placed objects, defining the angular orientationof the object, etc.). In another specific example, Block S200 caninclude simultaneously placing a plurality of objects into a 3D scene(e.g., generating a 3D scene composed of a plurality of objects).

In variations, the 3D scene generated in accordance with Block S200 caninclude a mixture of both procedurally generated geometry, as well asmodel libraries (E.g., sets of predetermined 3D models associated withsome object classes). For example, the buildings, road surface,sidewalks, traffic lights and poles can be entirely procedurallygenerated and/or individually unique (e.g., within a given scene, acrossa plurality of generated scenes, etc.), whereas model libraries can beused to select pedestrian, bicyclist, car and traffic sign objects(e.g., wherein the geometry can shared between all instances of theseobject classes, and properties such as placement, orientation andcertain texture and material aspects can vary between instances and begenerated based on values determined via LDS sampling according to avariation of Block S100).

In variations of Block S200, generating the 3D scene can includedetermining and/or executing a rule set that includes contextualarrangements and requirements between objects. For example, the rule setcan constrain pedestrian objects to be placed in crosswalks, and/orutilize a PDF that is weighted towards placement of pedestrians in acrosswalk with higher likelihood than placement outside of a crosswalk.In another example, the rule set can constrain vehicles to be placed ina roadway while allowing lateral placement, lane placement, and/ordirection to vary within respective parameter spaces or ranges. The ruleset can additionally or alternatively include any other suitable rulesor constraints around the placement or arrangement of objects in the 3Dscene.

Block S200 can include specifying an illumination of the 3D scene. Inexamples, the illumination of the scene can be specified by a sunposition (e.g., determined via a constrained LDS sampling) and caninclude a parametrized depiction of the sky (e.g., including cloudcover, air quality index, airborne particulates, etc.). Parametricspecification of the illumination functions to provide lightingconditions (e.g., at street level) within the 3D scene that include acontinuous range of times of day, all potential light directions (e.g.,relative to the ego vehicle, the virtual camera, etc.), as well asindirect light due to clouds and other participating media and/or lightsources. In examples, calculating the illumination of objects in thescene in accordance with Block S200 can be performed in a high dynamicrange, scene-referred linear RGB color space to provide realistic lightand contrast conditions for a virtual camera. However, the illuminationcan be otherwise suitably calculated.

Block S200 preferably includes instantiating a unique virtual world fora given image (e.g., in lieu of synthesizing a plurality of images of avirtual world that extends beyond the composition of a frame). This canbe made computationally efficient by generating the set of geometry thatis visible either directly to the virtual camera, or through reflectionsand shadows cast into the view of the virtual camera, without generatinga virtual world that extends beyond this limited scope (e.g., limited bythe viewability of the scene by a virtual camera).

3.3—Image Rendering

Block S300 includes generating a synthetic image of the generated scene,which functions to create a realistic synthetic two-dimensional (2D)representation of objects in the scene, wherein the objects areintrinsically labeled with the parameter values used to generate thescene (e.g., the objects in the scene, object classifications, thelayout of the objects, all other parametrized metadata, etc.). BlockS300 can also function to enhance realism in the illumination andmaterial interactions in the final synthetic image dataset byimplementing physically based light transport simulation. Block S300 canalso function to produce realistic synthetic images with pixel-perfectground truth annotations and/or labels (e.g., of what each object shouldbe classified as, to any suitable level of subclassification and/orincluding any suitable geometric parameter, such as pose, heading,position, orientation, etc.). Block S300 is preferably performed basedon a set of rendering parameters (e.g., determined in accordance with aninstance of a variation of Block S100), but can additionally oralternatively be performed based on a fixed set of rendering rules orprocedures. Block S300 is preferably performed by a virtual camera,wherein the viewpoint of the virtual camera is determined as a parametervalue in a variation of Block S100 (e.g., as a rendering parameter).Generating the synthetic image preferably includes generating aprojection of the 3D scene onto a 2D virtual image plane at apredetermined location in the 3D scene (e.g., at the virtual cameralocation).

In a specific example, Block S300 can include: stochastically generatingsample paths of virtual light rays in the image plane and tracing thesample paths through the 3D scene. The sample paths can be generatedaccording to sampling of an LDS, a random sequence, or any othersuitable sampling technique. At each interaction between the samplepaths and objects in the scene, light virtually scattered by theemitting objects are sampled and their contributions summed up. Thistechnique can provide accurate simulation of sensor characteristics andthe color filter array (CFA), the effect of the optical system (pointspread function/PSF, distortion, etc.), complex geometries andscattering at surface and in participating media. This technique canalso be parallelized and scaled efficiently, and enhanced through MonteCarlo importance-sampling techniques (e.g., quasi-Monte Carlo methods,importance-weighted sampling method, LDS sampling methods, etc.). Inanother specific example, the synthetic image can be generated byperforming ray tracing between the predetermined location and theobjects of the scene. In another example, the synthetic image can begenerated by topographically remapping the surfaces of the 3D scene ontoa 2D surface. In another example, Block S300 can be performed usingMonte Carlo-based light transport simulation coupled with simulation ofvirtual optics and sensors (e.g., camera lenses, CCD image sensors,etc.) to produce realistic images. In another example, Block S300 caninclude capturing a two-dimensional projection of a generated 3D scene(e.g., with or without incorporating realistic lighting effects and/orother light transport simulation). However, Block S300 can be otherwisesuitably implemented using any other suitable synthetic image generationtechnique.

Examples of parameters on which rendering can be based (e.g., renderingparameters, determined and/or sampled according to one or morevariations of Block S100) include: natural light source parameters(e.g., sun direction and height, time of day simulation, etc.),practical light source parameters (e.g., intensity of car headlights,street lights, building lights, etc.), environmental atmosphericparameters that can affect lighting (e.g., cloud cover, fog density,smoke, air quality, etc.), attributes of the 3D models that affect lightbehaviors (e.g., material type, textural variation, clean vs. rusty vs.dusty vehicles or other objects, concrete vs. asphalt road, objectcolors or markings or patterns, etc.), camera and/or lens parametersassociated with a virtual camera or other image sensor (e.g., viewdirection angle, field of view, focal length, lens distortion,aberrations, etc.), and any other suitable parameters related to imagerendering. In some examples, some of the aforementioned parameters canbe changed in subsequent Blocks of the method 100 (e.g., duringaugmentation in accordance with one or more variations of Block S400).

Determining rendering parameters can include selecting one of aplurality of 3D scenes (e.g., according to a selection parameter valuecompared against a map value as described in relation to Block S100),and rendering a synthetic image of one of the plurality of 3D scenesbased on the selection, to efficiently cover the set of generatedscenes.

The output of Block S300 preferably includes a two dimensional syntheticimage that realistically depicts a realistic 3D scene. The syntheticimage defines a set of pixels, and each pixel is preferably labeled withthe object depicted by the pixel (e.g., intrinsically labeled based onthe parameters used to generate the object rendered in the image). Inthis manner, a “pixel-perfect” intrinsically annotated synthetic imagecan be created. In alternative variations, labelling can be performed ona basis other than a pixel-by-pixel basis; for example, labelling caninclude automatically generating a bounding box around objects depictedin the image, a bounding polygon of any other suitable shape, a centroidpoint, a silhouette or outline, a floating label, and any other suitableannotation, wherein the annotation includes label metadata such as theobject class and/or other object metadata. Preferably, labelling isperformed automatically (e.g., to generate an automatically semanticallysegmented image); however, labelling can additionally or alternativelybe performed manually or semi-manually (e.g., wherein a user or operatorspecifies which objects to label and the pixels are automaticallylabeled if they depict a specified object, wherein a user can click onan object in the image and a bounding shape is automatically generatedabout the object, etc.); for example, a user can specify that pixelsdepicting vehicles are labeled with metadata describing the vehicletype, material properties, and the like, and that pixels that do notdepict a vehicle remain unlabeled. Semantic segmentation can beperformed with any suitable level of granularity, and labeled orannotated pixels can be grouped by any category or subcategory of labelor annotation (e.g., defined by the parameters used to procedurallydefine the scene in the image) in producing a segmentation of the image.For example, pixels can be semantically segmented by object class,object subclass, orientation, any other suitable geometric or otherparameter as determined in accordance with one or more variations ofBlock S100, and/or any suitable combination of the aforementioned.However, Block S300 can additionally or alternatively include anysuitable output.

3.4—Image Augmentation

The method can optionally include Block S400, which includes augmentingthe synthetic image. Block S400 functions to modify the image afterrendering. Block S400 can also function to reduce the tendency of modelsto overfit the synthetic image data when the synthetic image data isused as a training data set, by increasing the degree of variation ofthe training data (e.g., wherein variations are added to each syntheticimage to create multiple augmented synthetic images, before theresulting augmented images are passed to the network or model astraining data). Thus, Block S400 can also function to reduce the size ofthe dataset that can be needed to achieve a desired level of modelperformance. Block S400 can also function to enhance the realism of thesynthetic image by implementing modeled optical effects (e.g., usingpoint spread functions in the image domain). Block S400 is preferablyperformed based on a set of augmentation parameters, which arepreferably determined and sampled in accordance with an instance ofBlock S100; however augmentation can be otherwise suitably performedwith any other suitable basis.

Augmentation parameters used to vary (e.g., augment) the images inaccordance with Block S400 can include: translation parameters (e.g.,translations in x or y directions of a subframe of an image frame),scale parameters (e.g., zooming a subframe of an image frame),brightness and contrast parameters, and any other suitable parametersthat can affect the visible qualities of the synthetic image. Thedetermination and sampling of the augmentation parameters are preferablyperformed in the manner as described above in relation to Block S100(e.g., sampling the value of each augmentation parameter from an LDS,sampling the values of an augmentation parameter group from an LDS,etc.) to reduce unintended and/or undesired correlation across thesynthetic image dataset between samples of augmentation parameters togenerate augmentation parameter values; however, values of theaugmentation parameters can be otherwise suitably determined.

Examples of parameters on which augmentation can be based (e.g.,utilized to augment a synthetic image) include: image transformationparameters (e.g., brightness, dynamic range, etc.), geometrictransformation parameters (e.g., governing translation, rotation,scaling, flipping, etc.), optical simulation parameters (e.g., governinglens properties, parametrized optical distortions related to virtuallenses or other media, lens flare, chromatic aberrations, otheraberrations, PSF shape, etc.), simulated sensor or camera parameters(e.g., governing exposure level, sensor dynamic range, sensor blacklevel, light response curve, static noise, temporal noise, shot noise,photon noise, color filter array/CFA arrangement, CFA filtercharacteristics, demosaicing, etc.), and any other suitable parametersrelated to varying or altering the synthetic image subsequent torendering. Any of the aforementioned parameters can be defined accordingto a parametric function governing the associated property of the image,and the value can be sampled from an LDS (e.g., according to one or morevariations of Block S100) to generate an augmentation parameter valueused to augment the synthetic image in Block S400.

In variations, augmentation parameter ranges can be applied toaugmentation parameters prior to value determination (e.g., sampling).For example, maxima and minima associated with various parameters can beextracted from a real-world image dataset (e.g., maximum cameraexposure, minimum camera exposure, maximum and minimum sensor noise,etc.), and used to bound varied augmentation parameters to provideefficient coverage of the real-world parameter space (e.g., via LDSsampling) in the synthetic image dataset. In another example, a thirdparty can define sensor characteristic ranges and provide the ranges asan input to the method, and Block S400 can include augmenting thesynthetic image dataset to simulate the sensor performance viaparametric variation of the augmentation parameters. However, inadditional or alternative variations, augmentation parameter values canbe determined and applied to augment synthetic images while applying anysuitable constraints or parameter ranges in any suitable manner.

In variations, the method can omit Block S400 for one or more imagesthat are ultimately combined into a synthetic image dataset (e.g., inBlock S500). For example, the method can include augmenting a subset ofa total number of synthetic images and leaving a second subsetun-augmented. In another example, the method can include generating thesynthetic image dataset without augmenting any of the images afterrendering.

3.5—Dataset Generation

Block S500 includes generating a synthetic image dataset. Block S500functions to output a synthetic image dataset, made up of intrinsicallylabelled images, as a result of the procedural generation, rendering,and/or augmentation Blocks of the method, for use in downstreamapplications (e.g., model training, model evaluation, image capturemethodology validation, etc.). Block S500 can thus also includecombining a plurality of images into dataset (e.g., made up of theplurality of images). Block S500 can include repeating Blocks S100,S200, S300, and S400 to build up a synthetic dataset of syntheticimages. Repetition of the aforementioned Blocks can be performed anysuitable number of times, to produce a synthetic image dataset of anysuitable size. The predetermined number of iterations can be: selectedby a user (e.g., an end user of the dataset), based upon the parameterranges of one or more parameters (e.g., wherein a larger parameter rangecan correspond to a larger number of iterations and larger resultingdataset, to prevent sparse sampling).

Block S500 can include combining synthetic and real images into acombined image dataset. The combined image dataset can have variousrelative percentages of synthetic versus real images (e.g., 50%synthetic and 50% real, 20% synthetic and 80% real, 90% synthetic and10% real, etc.); in some variations, the relative percentages can bedetermined based on the end-use application (e.g., for cases wherein theend-use application includes evaluating a model that was trained onreal-world data, a large percentage of synthetic data can be used toartificially increase the percentage of “edge cases” presented by theevaluation data), based on the desired dataset size (e.g., wherein thereare insufficient real images to provide an adequate desired datasetsize, and the remainder are produced via synthetic image generation), orotherwise suitably determined.

Block S500 can include reordering images (e.g., from the order in whichthe synthetic images were produced in cases wherein the images areproduced sequentially, from an initial ordering, etc.) to prevent modelhysteresis during training (e.g., wherein trained model outputs aredependent upon the order of presentation of images during training).Reordering the images can include tagging each of a set of images withan ordering parameter (e.g., a sequential ordering parameter), the valueof which can be randomly generated, sampled from an LDS, or otherwisesuitably determined.

In a first variation, all the parameters defining the final image (e.g.,scene generation parameters associated with Block S200, renderingparameters associated with Block S300, and augmentation parametersassociated with Block S400) are varied (e.g., resampled from an LDS,determined in accordance with one or more variations of Block S100 inmultiple instances) for each synthetic image. By utilizing an LDS todetermine the parameter values anew for each image, this variationpreferably maximizes the variation among the set of images generated,given a set of parameters to vary. Alternatively, the variation may notbe maximized, and/or an LDS may not be utilized, for applicationswherein the widest variation is not desired (e.g., wherein a constrainedset of synthetic image parameters is desired). In a second variation, asingle scene parameter is varied (e.g., resampled from an LDS) and theremainder are held constant during synthetic image generation.Preferably, in the second variation, the single parameter varied is notthe camera position (e.g., viewpoint); alternatively, the singleparameter can be the camera position. However, the synthetic imagedataset can be otherwise suitably generated from one or more syntheticimages.

3.6—Model Training

The method can include Block S600, which includes training a model basedon the synthetic image dataset. Block S600 functions to train a learningmodel (e.g., an ML model, a synthetic neural network, a computationalnetwork, etc.) using supervised learning, based on the intrinsicallylabeled synthetic image dataset. Block S600 can function to modify amodel to recognize objects (e.g., classify objects, detect objects,etc.) depicted in images with an improved accuracy (e.g., as compared toan initial accuracy, a threshold accuracy, a baseline accuracy, etc.).Block S600 can also function to augment a model trained on real-worlddata with synthetic data representative of “edge cases” (e.g., rareevents that occur at low frequency, or not at all, in real-world datasets). Block S600 is preferably based on the synthetic dataset havingintrinsic labels (e.g., object metadata embedded as a result ofprocedural scene generation), but can additionally or alternatively bebased on any suitable data having any other suitable labels. The typesof models trained in Block S600 can include one or more of: supervisedlearning models based on empirical risk minimization, structural riskminimization, generative training, and any other suitable learningmodels. Approaches to train the models can include: analytical learning,artificial NN (e.g., CNN), backpropagation, boosting, Bayesianstatistics, case-based reasoning, decision tree learning, inductivelogic programming, Gaussian process regression, group method of datahandling, kernel estimators, learning automata, learning classifiersystems, minimum-message-length estimation, multilinear subspacelearning, Naive Bayes classifier, maximum entropy classifier,conditional random field, nearest neighbor algorithm, probablyapproximately correct learning, ripple down rules, symbolic machinelearning algorithms, subsymbolic machine learning algorithms, supportvector machines, minimum complexity machines, random forests, ensemblesof classifiers, ordinal classification, data pre-processing, imbalanceddataset handling, statistical relational learning, fuzzy classificationalgorithms, and any other suitable approaches. Alternatively, models canbe trained utilizing unsupervised learning, and/or any other suitablelearning process.

In a specific example, the method includes training a dilated fullyconvolutional network (DFCN) using a synthetic image dataset produced inaccordance with Blocks S100-S500, and a real-image dataset (e.g.,organic data). The DFCN can be trained using stochastic gradient descentwith a learning rate of 10⁻⁵, momentum of 0.99 and a batch size of 8(e.g., for synthetic image data samples). For organic data, a learningrate of 10⁻⁴ can be used in baseline training and 10⁻⁵ in fine-tuning,with the same momentum and batch size. However, any suitable learningrate, momentum, and/or batch size can be used in training a DFCN. Inthis example, 40K iterations can be used during frontend baselinetraining, looK iterations for frontend fine tuning and 60K iterationsfor context baseline training; however, any suitable number ofiterations can be used for any suitable training portion in relatedexamples.

In another specific example, the method includes training afull-resolution residual network (FRRN). This network can be trainedwith no weight initialization, using the same dataset combinations asabove in relation to the DFCN. The FRRN can be trained with a learningrate of 10⁻³ for organic data and 10⁻⁴ for synthetic data. The bootstrapwindow size can be set to any suitable sample length (e.g., 512 fororganic data, 8192 for synthetic data, etc.). The batch size ispreferably 3, but can additionally or alternatively be any suitablesize. In this example, 100K iterations can be used both during baselinetraining and fine tuning, but in related examples any suitable number ofiterations can be used.

3.7—Model Evaluation

The method can include Block S700, which includes evaluating a modelbased on the synthetic image dataset. Block S700 can include generatinga performance metric that quantifies the performance of the model atvarious tasks (e.g., object classification, object detection, etc.)using the synthetic dataset as an input. Block S700 functions to testthat a previously trained model performs as desired, required, and/orexpected when provided with the synthetic dataset as an input. BlockS700 is preferably performed after a model is trained on a datasetdistinct from the synthetic dataset generated in Block S135 (e.g.,another synthetic dataset generated in another instance of Block S135, areal-world dataset, etc.). Block S700 is also preferably based on asynthetic dataset with intrinsic labels (e.g., object metadata embeddedas a result of scene generation). However, Block S700 can be otherwiseperformed at any suitable time and based on any suitable dataset (e.g.,a synthetic dataset generated in the same instance of Block S135) havingany suitable labels (e.g., manually generated labels, no labels, etc.).

In a first variation, Block S700 can include validating that the outputof a model is consistent for identical and/or similar inputs. Forexample, a machine learning model (e.g., a CNN) for classifying vehicletypes and behaviors is trained on a standardized real-worldtraffic-environment dataset. In this variation of Block S700, the modelis provided a synthetic dataset generated in accordance with a variationof the method as an input, wherein the synthetic dataset includes imagesof objects (e.g., of similar types as those in the real-world dataset)that are programmatically generated so as to provide the widest possiblerange of underlying parameter values in the fewest number of syntheticimage frames. The output of the model for the synthetic dataset is thencompared to the ground truth (e.g., the intrinsic labels) of thesynthetic dataset, and the consistency of the model is thus determinedbased on the comparison. However, validating the model output using asynthetic image dataset can be otherwise suitably performed.

Block S700 can include evaluating the comparative performance (e.g., inobject detection, classification, etc.) of a model trained utilizingsynthetic data alone versus utilizing organic or real-image data, orreal-image data in combination with synthetic data.

In relation to Block S700, evaluated performance can be quantified usingthe intersection over union (IoU) metric (e.g., for objectclassification), mean squared error (MSE) metric, root MSE metric,squared error metric, prediction confidence interval metrics, precisionmetrics, recall metrics, lift scores or lift metrics, accuracy metrics,loss metrics, and/or any other suitable network performance metrics.

In variations, Block S700 can include generating a performance metricthat is used to modify the synthetic image dataset (e.g., wherein thesynthetic image dataset is modified based on the relationship betweenthe performance metric and a threshold). For example, the method caninclude generating additional synthetic images (e.g., according tovariations of Blocks S100-S400) based on the performance metric fallingbeneath a threshold, combining the additional synthetic images with thesynthetic image dataset (e.g., adding images, replacing existing imagesrandomly, non-randomly, etc.), until the performance metric exceeds thethreshold (e.g., based on subsequent and iterative model evaluation).However, the synthetic image dataset can additionally or alternativelybe modified in any suitable manner based on the performance metric(e.g., augmented, re-rendered, re-generated, etc.).

3.8—Additional Method Examples

In a first specific example implementation of the method, as shown inFIG. 4, a set of parameter values is determined. Determining theparameter values in this example includes: computing a ground surfaceparameter based on a stochastic variable (e.g., fractal noise);constructing a graph network made up of a set of graph vertices andedges representative of a road network; determining the type of roadmarkings (e.g., as a discrete variable), the amount of weathering and/orwear of the road (e.g., as a continuous variable), and the materialproperties of the road (e.g., as a continuous variable); generating aset of virtual buildings by positioning a footprint (e.g., selected froma set of predetermined building footprints) adjacent to the virtualroadway, determining the number of floors (e.g., as a discretevariable), height of each floor (e.g., as a continuous variable), thenumber of windows per floor (e.g., as a discrete variable), and the sizeof each window (e.g., as a continuous variable); selecting a number ofpedestrians (e.g., as a discrete variable), selecting (for each of thenumber of pedestrians) one out of a set of predetermined 3D pedestrianmodels (e.g., as a discrete variable), orienting and positioning eachindividual pedestrian model (e.g., as continuous and stochasticvariables, respectively); selecting a number of cars, bicyclists,trucks, and buses (e.g., as a discrete variable), selecting (for eachvehicle) one out of a set of predetermined 3D models (e.g., as adiscrete variable), positioning (e.g., as a stochastic variable) eachindividual vehicle in an orientation dependent on the traffic flow ateach position (e.g., a truck on the righthand side of the virtual roadis oriented substantially parallel with and facing the direction ofproper traffic flow); selecting a number of trees, street lights,traffic signs, and traffic signals (e.g., as discrete variables), andrepeating the parameter value determination for each of these types ofobjects; selecting a texture map of the virtual sky (e.g., as a discretevariable) and orienting the texture (e.g., as a continuous variable) tomaximize coverage of the gamut of realistic lighting conditions;determining a virtual camera viewpoint to lie on an edge of the roadnetwork graph (e.g., as a discrete variable), and having a randomposition in the righthand lane of the virtual road network (e.g., as astochastic variable).

In determining the parameter values described above in the firstspecific example, each value is sampled from an N-dimensional LDS,wherein N is equal to the number of parameters. However, in relatedexample implementations, multiple M-dimensional LDSs can be used tosample the parameter values, wherein M is equal to the number ofparameters in subsets (e.g., groups) of the total number of parameters.Subsets of the parameters need not be of the same size, but canadditionally or alternatively be of the same size (e.g., number ofparameters in each subset).

Generating the scene in this example includes: rendering the groundsurface, superimposing the road graph onto the ground surface (e.g.,using the defined number of lanes as a discrete variable, the road widthas a continuous variable, the presence or absence of a median andparking spaces as discrete variables, and integrating the sampled valuesinto the generation of the road graph network); rendering each buildingaccording to the determined building parameters; rendering the set ofvirtual pedestrians based on the determined pedestrian parameters; andrendering the vehicles, trees, street lights, traffic signs, trafficsignals, virtual sky, etc., according to the determined parameter valuesfor the respective objects. This example of the method includesgenerating 25,000 synthetic images by repeating the determination of theparameter values according to the constructed LDS(s), and generating thescene anew according to the parameter values thus determined, andcapturing a synthetic image (e.g., via a ray tracing technique betweenthe virtual objects of the scene and the virtual camera viewpoint) ofeach instance of the generated scene. In related examples, the scene isgenerated fewer than 25,000 times, and at least two of the syntheticimages are generated of the same generated scene. However, any suitablenumber of synthetic images can be generated based on any suitable numberof generated scenes.

In a second specific example of the method, a synthetic image dataset isgenerated in accordance with a variation of the method. After generatingthe synthetic image dataset (e.g., by repeatedly performing variationsof Blocks S100-S300), this example of the method includes testing apreviously trained convolutional neural network (CNN) model that wastrained to classify objects on and/or around a roadway (e.g., vehicles,pedestrians, background scenery, etc.). In this example, testing themodel includes: providing the synthetic image dataset to the CNN as aninput, classifying objects within the dataset using the model togenerate a set of object labels, comparing the set of object labelsoutput by the CNN to the predetermined (e.g., intrinsically known)labels of each object depicted in the synthetic image dataset, andevaluating the successful classification rate of the CNN based on thecomparison between the set of object labels and the predeterminedlabels.

In a third specific example, the method includes determining an objectclass (e.g., for inclusion in a 3D scene); determining a geometricparameter (e.g., having a first parameter space); sampling the firstparameter space according to a first low discrepancy sequence (LDS) togenerate a geometric parameter value; generating a three-dimensional(3D) scene including an object (e.g., an instance of the determinedobject class) by arranging the object based on the geometric parametervalue; determining a rendering parameter (e.g., having a secondparameter space); sampling the second parameter space according to asecond LDS to generate a rendering parameter value; rendering asynthetic image of the 3D scene (e.g., made up of a set of pixels, someof which depict the object) based on the rendering parameter value;automatically labelling each pixel depicting the object within the imagewith a label (e.g., labeling the object with its object class, othermetadata, etc.); determining an augmentation parameter (e.g., having athird parameter space); sampling the third parameter space according toa third LDS to generate an augmentation parameter value; augmenting thesynthetic image based on the augmentation parameter value to generate anaugmented synthetic image; and combining the augmented synthetic imagewith a set of augmented synthetic images to generate a synthetic imagedataset (e.g., made up of intrinsically labelled images).

In a fourth specific example, the method includes determining a set ofparameters defining a multidimensional parameter space (e.g., includinggeometric parameters, rendering parameters, augmentation parameters,etc.); determining a set of parameter values corresponding to the set ofparameters (e.g., via sampling the multidimensional parameter spaceaccording to an LDS); generating a plurality of 3D scenes using theparameter values (e.g., geometric parameter values); rendering asynthetic image of one of the plurality of 3D scenes using the set ofparameter values (e.g., rendering parameter values), including selectingwhich of the 3D scenes to render based on one of the parameter values;augmenting the synthetic image using the parameter values (e.g.,augmentation parameter values) to generate an augmented synthetic image;and combining the augmented synthetic image with a set of augmentedsynthetic images to generate a synthetic image dataset (e.g., whereinthe set of augmented synthetic images is generated by repeatedlyrendering and augmenting images of generated 3D scenes for apredetermined number of repetitions).

In a fifth specific example, the method includes selecting a first setof object classes associated with traffic objects; defining a set ofgeometric parameters associated with the first set of object classes;selecting a second set of object classes from the first set of objectclasses, wherein each of the second set of object classes corresponds toa set of predetermined 3D models associated with a map value (e.g.,between 0 and 1); sampling a set of parameter values corresponding tothe set of geometric parameters and a set of map values (e.g., accordingto an LDS); selecting one of the set of predetermined 3D modelscorresponding to each of the second set of object classes based on acorresponding map value; and generating a 3D scene, the composition(e.g., scene composition) of which includes a plurality of objects basedon the set of parameter values, wherein each of the plurality of objectsis an instance of the first set of object classes, wherein each of theplurality of objects is arranged within the 3D scene based on the set ofparameter values of the set of geometric parameters, and wherein each ofthe plurality of objects corresponding to an instance of the second setof object classes is generated using one of the set of predetermined 3Dmodels.

In examples, the method can be applied to produce synthetic data as anoutput of variations of Block S200, S300, and/or S400. For example, aset of scenes generated in accordance with one or more variations ofBlock S200 can be provided (e.g., to a third party) without subsequentimage rendering and/or augmentation. In another example, a single staticscene (e.g., of particular relevance to an end-user application) can beused to render many image variations, which can be augmented or leftun-augmented post-rendering. In another example, stand-alone parameterexploration in the context of augmentation alone can be used (e.g., totrain ML systems and models) with real data (e.g., to perform efficientcoverage of the augmentation-specific parameter space and augment areal-image dataset using such efficiently determined augmentationparameters sampled using an LDS as in one or more variations of BlockS100).

The systems and methods of the preferred embodiment and variationsthereof can be embodied and/or implemented at least in part as a machineconfigured to receive a computer-readable medium storingcomputer-readable instructions. The instructions are preferably executedby computer-executable components preferably integrated with the systemand one or more portions of a processor and/or a controller 430. Thecomputer-readable medium can be stored on any suitable computer-readablemedia such as RAMs, ROMs, flash memory, EEPROMs, optical devices (CD orDVD), hard drives, floppy drives, or any suitable device. Thecomputer-executable component is preferably a general or applicationspecific processor, but any suitable dedicated hardware orhardware/firmware combination device can alternatively or additionallyexecute the instructions.

Although omitted for conciseness, the preferred embodiments includeevery combination and permutation of the various Blocks of the method100 and/or associated physical components (e.g., processing systems,CPUs. GPUs, etc.). Blocks can be executed iteratively or serially.Blocks can be executed in any suitable order, and multiple instances ofeach Block can be executed in a single iteration of the method.

As a person skilled in the art of image analysis and synthetic imagegeneration will recognize from the previous detailed description andfrom the figures and claims, modifications and changes can be made tothe preferred embodiments of the invention without departing from thescope of this invention defined in the following claims.

What is claimed is:
 1. A method for synthetic data generation andanalysis comprising: determining an object class; determining ageometric parameter, wherein the geometric parameter defines a firstparameter space; sampling the first parameter space according to a firstlow discrepancy sequence (LDS) to generate a geometric parameter value;generating a three-dimensional (3D) scene comprising an object, whereinthe object is an instance of the object class, wherein generating the 3Dscene comprises arranging the object based on the geometric parametervalue; determining a rendering parameter, wherein the renderingparameter defines a second parameter space; sampling the secondparameter space according to a second LDS to generate a renderingparameter value; rendering a synthetic image of the 3D scene based onthe rendering parameter value, wherein the synthetic image defines a setof pixels and depicts the object within a subset of the set of pixels;automatically labelling each pixel of the subset of the set of pixelswith a label defining the object class; determining an augmentationparameter, wherein the augmentation parameter defines a third parameterspace; sampling the third parameter space according to a third LDS togenerate an augmentation parameter value; augmenting the synthetic imagebased on the augmentation parameter value to generate an augmentedsynthetic image; and combining the augmented synthetic image with a setof augmented synthetic images to generate a synthetic image datasetcomprising intrinsically labelled images.
 2. The method of claim 1,further comprising limiting a resolution of at least one of the firstparameter space, the second parameter space, and the third parameterspace to reduce a dimensionality of the synthetic image data set.
 3. Themethod of claim 2, further comprising training a machine-learning model,based on the intrinsically labeled images of the synthetic imagedataset.
 4. The method of claim 1, further comprising classifyingobjects depicted in the synthetic image dataset using a trainedmachine-learning model to generate a performance metric.
 5. The methodof claim 4, further comprising modifying the synthetic image datasetbased on the performance metric.
 6. The method of claim 1, wherein thefirst LDS comprises a first Sobol sequence, the second LDS comprises asecond Sobol sequence, and the third LDS comprises a third Sobolsequence.
 7. A method for synthetic data generation and analysiscomprising: determining a set of parameters defining a multidimensionalparameter space, wherein the set of parameters comprises a set ofgeometric parameters, a set of rendering parameters, and a set ofaugmentation parameters; determining a set of parameter valuescorresponding to the set of parameters, wherein determining the set ofparameter values comprises sampling the multidimensional parameter spaceaccording to a low discrepancy sequence (LDS); generating a plurality ofthree-dimensional (3D) scenes based on the set of parameter valuescorresponding to the set of geometric parameters; rendering a syntheticimage of one of the plurality of 3D scenes based on the set of parametervalues corresponding to the set of rendering parameters, wherein atleast one of the set of rendering parameters comprises a selection ofone of the plurality of 3D scenes; and augmenting the synthetic imagebased on the set of parameter values corresponding to the set ofaugmentation parameters to generate an augmented synthetic image; andcombining the augmented synthetic image with a set of augmentedsynthetic images, wherein the set of augmented synthetic images isgenerated by repeating rendering and augmenting synthetic images for apredetermined number of repetitions, to generate a synthetic imagedataset.
 8. The method of claim 7, further comprising classifyingobjects depicted in the synthetic image dataset using a trainedmachine-learning model to generate a performance metric.
 9. The methodof claim 7, wherein sampling the multidimensional parameter spacecomprises performing a Cranley-Patterson rotation between at least twodimensions of the multidimensional parameter space.
 10. The method ofclaim 7, wherein the LDS comprises one of a Sobol sequence, a Haltonsequence, and a Hammersley sequence.
 11. The method of claim 7, furthercomprising combining the synthetic image dataset and a real imagedataset.
 12. The method of claim 11, further comprising training anobject classification model based on the combination of the syntheticimage dataset and the real image dataset.
 13. A method for syntheticdata generation and analysis comprising: selecting a first set of objectclasses associated with traffic objects; defining a set of geometricparameters associated with the first set of object classes; selecting asecond set of object classes from the first set of object classes,wherein each of the second set of object classes corresponds to a set ofpredetermined three-dimensional (3D) models associated with a map valuebetween 0 and 1; sampling a set of parameter values corresponding to theset of geometric parameters and a set of map values, wherein each of theset of parameter values and each of the set of map values is sampledaccording to a first low-discrepancy sequence (LDS); selecting one ofthe set of predetermined 3D models corresponding to each of the secondset of object classes based on a corresponding map value; and generatinga 3D scene composed of a plurality of objects based on the set ofparameter values, wherein each of the plurality of objects comprises aninstance of the first set of object classes, wherein each of theplurality of objects is arranged within the 3D scene based on the set ofparameter values of the set of geometric parameters, and wherein each ofthe plurality of objects corresponding to an instance of the second setof object classes is generated based on the one of the set ofpredetermined 3D models corresponding to each of the second set ofobject classes.
 14. The method of claim 13, further comprisingoffsetting a sample index of each of the set of parameter values andeach of the set of map values by a randomly generated digit betweensampling of each of the set of parameter values and each of the set ofmap values according to the first LDS.
 15. The method of claim 13,wherein the LDS comprises one of a Sobol sequence, a Halton sequence,and a Hammersley sequence.
 16. The method of claim 13, furthercomprising defining a set of rendering parameters, and sampling the setof rendering parameters according to a second LDS to generate a set ofrendering parameter values; rendering a synthetic image of the 3D scenebased on the set of rendering parameter values; and combining thesynthetic image with a set of synthetic images to generate a syntheticimage dataset.
 17. The method of claim 16, further comprising generatinga plurality of 3D scenes, wherein one of the set of rendering parameterscomprises a scene selection parameter, and selecting the 3D scene priorto rendering based on the scene selection parameter.
 18. The method ofclaim 16, further comprising classifying objects depicted in thesynthetic image dataset using a trained machine-learning model togenerate a performance metric.
 19. The method of claim 16, furthercomprising: extracting, from a real image dataset, a set of augmentationparameter ranges corresponding to a set of augmentation parameters;sampling the set of augmentation parameters according to a third LDS togenerate a set of augmentation parameter values; augmenting thesynthetic image, prior to combining the synthetic image with the set ofsynthetic images, based on the set of augmentation parameter values togenerate an augmented synthetic image; and combining the augmentedsynthetic image with the set of synthetic images to generate thesynthetic image dataset, wherein set of synthetic images comprises a setof augmented synthetic images.
 20. The method of claim 19, furthercomprising training an object classification model based on acombination of the synthetic image dataset and the real image dataset.